Method for making a heat exchanger



March 21, 1957 E. P. ODDY ET AL 3,399,763

METHOD FOR MAKING A HEAT EXCHANGER Original Filed Dec. 20, 1962 3Sheets-Sheet 1 In venibro and March 21, 1957 Original Filed Dec. 20,1962 z srAr/alv E. P. ODDY ET AL k E v,

METHOD FOR MAKING A HEAT EXCHANGER 5 Sheets-Sheet 2 In venj'arts' March21, 1967 p, ODDY ET AL 3,3@9,763

METHOD FOR MAKING A HEAT EXCHANGER Original Filed Dec. 20, 1962 5Sheets-Sheet 3 4 227672250715" fdwarcifodajy and JO/7:517, ffz'raaz a 2"QUE/f (7 2 United States Patent Ofifice 3,309,763 Patented Mar. 21, 19673,309,763 METHOD FOR MAKING A HEAT EXCHANGER Edward P. Oddy and LubomyrKinal, Detroit, Mich, as-

signors to Borg-Jamar Corporation, Chicago, Ill., a corporation ofIllinois Original application Dec. 20, 1962, Ser. No. 246,069, nowPatent No. 3,182,481, dated May 11, 1965. Divided and this applicationOct. 29, 1964, Ser. No. 413,675

4 Claims. (1. 29--157.3)

This application is a division of application, Ser. No. 246,069, EdwardP. Oddy et al., entitled, Heat Exchanger and Method of Its Manufacture,filed Dec. 20, 1962, and now US Patent No. 3,182,481.

This invention relates to a self-stacking fin structure for tube and finheat exchangers and methods for manufacturing the same.

Self-stacking fins for radiators and the like are known, for example, inKrackowizer, US. Patent No. 2,047,207. Radiators of this type areassembled in a conventional manner by arranging a plurality of coolingfins in generally parallel relation, inserting a series of fluidconducting tube elements through apertures provided in said fins, andthen joining opposite ends of the tubes to header assemblies above andbelow the fin structure. The assembled unit is then soldered or brazedto join the several elements together into a unitary structure.

One particular problem present in prior art structures is the tendencyof the fins to deform under pressure while being handled during assemblyor in other stages of manufacture. A principal cause of this problem isthat the spacer elements used to separate the fins from one another havenot been rigid enough to withstand anything but the most carefulhandling. This problem is especially present in the production ofradiator fins of the type employing a relatively thin metal fin stock onthe order of .0025.003 inch. Since the most acceptable fin stock mustnecessarily have a high coeflicient of thermal conductivity, the choiceof materials is usually either copper or aluminum, both of which areeasily deformed.

It is another object of the invention to provide an improved method ofmanufacturing tube and fin heat exchan ers, either in a continuousprocess or by utilizing individual fin elements.

Gther and more particular objects and advantages of the presentinvention will be apparent from the following detailed description andthe appended drawings, wherein:

FIGURE 1 is a front elevational view of a heat exchanger constructed inaccordance with the principles of the present invention;

FIGURE 2 is a top plan view of a portion of a heat exchanger fin elementused in the heat exchanger illustrated in FIGURE 1;

FIGURE 3 is an end view of the portion of a fin element taken alongsection lines 33 of FIGURE 2;

FIGURE 4 illustrates a second embodiment of a fin element;

FIGURE 5 illustrates a third embodiment of a fin element;

FIGURE 6 is an isometric View of a punch and die assembly employed toform the single self spacers illustrated in FIGURES 2, 3, and 4;

- IGURE 7 is a detailed view of the male punch element used in theassembly of FIGURE 6;

FIGURE 8 is a view of a punch assembly used to form the self spacersillustrated in FIGURE 5;

FIGURE 9 is a detailed elevational view of the male punch of FIGURE 8;

FIGURE 10 is a schematic illustration of a continuous manufacturingprocedure for assembly of the fin stock;

FIGURE 11 is a top plan view, partly schematic, of

the assembly process, at various stages, and is related to FIGURE 10;

FIGURE 12 is a detailed top plan view of the fin stock prior to thefolding operation;

FIGURE 13 is the preferred configuration of the spacer lug as viewedalong lines 13l13 in FIGURE 3; and

FIGURES 14, 15, and 16 illustrate alternate embodiments of the spacerelements.

Referring now to FIGURE 1, a heat exchanger generally indicated by thenumeral 1 is shown having supply and receiving headers 2 and 3interconnected by a plurality of tubes 5. The tubes, in a preferredembodiment, are of the flat type to reduce the resistance to air flowthrough the unit although it should be understood that they may have anycross-sectional configuration desired. Arranged parallel to the headers2 and 3 are a plurality of fin elements 7 having apertures 8, FIGURE 2,for the reception of the tubes 5. In order to space the fin elements toafford the self-stacking capability a plurality of spacers or lugs 10are provided, said spacers being formed from the fin sheets by punchingout or extruding a small, rectangular shaped section of said sheet andbending the same to a position perpendicular to the plane of the fin.Each tube aperture 8 includes a surrounding flange to insure a moresecure connection between the fins and the tubes. The fins may beconnected to the tubes in any well known manner, but it is expeditiousto use a soldering or brazing process. 1

As shown in FIGURE 2, each fin element includes a series of spacedelongated tube apertures 8 arranged in rows running lengthwise of thefin. The tube apertures in one row are preferably staggered with respectto the other row to increase the effective area of heat exchange.

Referring now in more detail to the tube spacers, each said spacer isformed by cutting an aperture in a strip of fin stock such that thematerial in the aperture is not severed completely from the fin stockand by bending or extruding the unsevered aperture material upwardly ordownwardly with respect to the strip. The edges of each spacer arecurled back or convoluted toward each other so that it provides one edgeintegrally connected to the fin itself and another edge adapted tocontact the fin element immediately above or below it. A very importantaspect of the present invention consists in the curling of the outerends of the spacer element around toward each other. By means of thisfeature an extremely rigid element is formed which resists deformation.

In the embodiment shown in FIGURE 2, the spacer elements are positionedbetween adjacent tube apertures in each row so that the spacers arestaggered with respect to each other. By positioning each spacer elementimmediately in front of one of the tubes, the resistance to flow causedby the spacer elements is not significantly greater than that caused bythe tubes themselves. While not required, it has been found to bedesirable to provide turbulizer elements spaced around each fin spacer.These turbulization elements form no part of the present invention andare to be regarded as purely optional.

As shown in FIGURE 4, an alternative design may include the spacerelements formed by punching the edge of the fin stock so that the spacerelements are spaced slightly inwardly from the edge. Variouscombinations of the edge design and the design shown in FIGURE 2, arecontemplated. For example, the spacers might be placed at randomthroughout the available space not taken up by the tube apertures. Thespacers, moreover, may be oriented longitudinally or transversely withrespect to the fin or may be located at any angle with respect to thelongitudinal axis of said fin element. It is further contemplated thatthe edge spacers (FIGURE 4) may be combined with the centrally disposedspacers (FIGURE 2) and may include various combinations of the randomlyoriented spacers.

FIGURE 5 illustrates a third embodiment of a spacer element whichcomprises a double spacer element having lugs arranged in pairs. Byusing a special punch, to be described below, both lugs are formed by asingle punching operation.

In FIGURES 6 and 7 a punch assembly adapted to form the single lugspacer elements shown in FIGURES 2, 3, and 4 is disclosed. This punchassembly includes a die plate 12 having a rectangular opening 14extending therethrough, a base plate 16, and a punch 18 carried by saidbase plate extending perpendicular to said base plate. A conventionalstripper plate (not shown) may be provided to facilitate withdrawal ofthe punch from the fin stock after the spacer element has been formed.The punch 18, shown in greater detail in FIGURE 6, comprises abifurcated member having a pair of sharp cutting prongs 22 on oppositesides thereof and face 24 sloping downwardly from a transverselyextending cutting edge 26. As the punch element is forced through thefin stock, the pair of cutting prongs 22 cut the strip at opposite endsof an imaginary rectangular section in the strip. As the punch isfurther extended through the strip, the transversely extending cuttingedge 26 engages the strip cutting the third side from the rectangularelement. Further movement of the punch causes the spacer element to beengaged by the sloping face 24 and is bent upwardly from the plane ofthe strip. Throughout this entire operation, the edges of the spacerelement are bent inwardly toward each other to provide the configurationdiscussed above having improved rigidity characteristics. This punchelement results in the spacer element being produced, i.e., pierced andformed with a single tool and with a single stroke of said tool.

The punch assembly employed for forming the double lug spacer element(FIGURE 5) is illustrated in FIG- UR'ES 8 and 9. The double lug punchdesign, which may be regarded as a paired set of single lug punches,comprises a punch body 20 having front, rear, and side faces 20a, 20b,and 200 respectively. A slot 21 extending through one end of the punchbody 20 from the front face 20a to the rear face 2% divides the end ofthe punch body into two substantially identical single lug punches eachof which includes a bifurcated member 27 having a pair of spaced cuttingprongs 22a, a transversely extending cutting edge 26a, and a face 24asloping downwardly from said cutting edge to the side faces of the punchbody. The operation of the punch is substantially the same as thatdescribed above in connection with the single lug punch, the onlydifference being that a slug or blank 27 is formed between the twotransversely extending cutting edges 26a as the spacer lugs are bentupwardly from the plane of the strip to positions on opposite sides ofthe aperture formed by the punch.

FIGURES 10 illustrates, in diagrammatic form, a continuous process formanufacturing the fin assemblies of the present invention. FIGURES 11and 12 which illustrate the strip of fin stock at various stagescorresponding to operations performed during the manufacturing processmay also be referred to for a complete understanding of the process.

Referring first to FIGURE 10, a continuous strip of thin metal fin stockis fed from a first station, where it is stored in a roll or any otherconvenient manner, and delivered to a second station where a pluralityof longitudinally spaced groups of slits 30, 31 (FIGURE 11) are formedtherein. This operation may be performed by a plurality of reciprocatingknives 35, 36.

Each group of slits comprises a series of spaced, coaligned individualslits 30a, 31a running transversely from one edge of the strip towardthe other so as to provide a series of unsevered portions 30b, 3111between the ends of the slits. In a preferred embodiment, the slit ofone group are staggered or offset with respect to the slits of anadjacent group so that the unsevered portions are similarly staggered.

After the slits are formed, the fin stock is fed to a third stationwhich is provided with a die press 40. The operation of the die press isintermittent and in timed relation with respect to the movement of thefin stock so that the die press performs its operations on alternatespaced apart areas A between adjacent groups of slits. The first diepress 40, arranged so that the punches and other forming elements moveupwardly into the strip, carries out the following operations: (1) Thetube apertures 8 are formed so that a narrow flange surrounding eachaperture extends upwardly from the plane of the strip; (2) The spacerelements, which may be of any previously described design, are formed sothat these also extend upwardly from the plane of the strip; and (3) Aseries of relatively short, longitudinally extending slits are provided,each said slit intersects the terminal portions of the transverselyextending slits to Provide a series of integral tie elements joiningadjacent sections of the fin stock. These tie elements may be formed bya double pronged punch element similar to that shown in FIGURES 6 and 7so as to obtain a convoluted reinforcing edge similar to those on thespacing lugs.

At a fourth station, the same operations performed at the third stationare repeated by die press 41, but the die press punching and cuttingelements all operate downwardly on the fin stock on the remainingalternate areas A thereof. Thus, the spacer elements, the tube apertureflanges, and the tie elements alternately extend downwardly and upwardlyfrom the plane of the strip throughout its length.

At a fifth station, the strip is bent alternately in opposite directionsalong the lines coincident with the transversely extending slits to forma corrugated or pleated pattern with the tube apertures in therespective fin plates coaxially arranged. Since alternate areas areprovided with oppositely extending tube flanges and spacing lugs, afterthe strip is folded, the flanges and lugs will all extend in the samedirection. After the fin plates have been gathered and formed into thecompressed arrangement shown at the left of FIGURE 10, the tubes areinserted through the coaxially arranged tube apertures, the headers areconnected to the opposite ends of the tube apertures, and then theassembly is bonded together in a unitary construction by brazing,soldering, or some equivalent method.

FIGURE 12, a detailed plan view of a section of the Strip just prior tothe folding operation, illustrates the optional turbulizer elements 43.The latter merely comprise small polygonal shaped apertures, formed withragged edges, said edges extending generally perpendicular to the planeof the fin plates. The ragged edges disrupt the flow of air past the finplates and prevent laminar flow of air past said plates therebyincreasing the heat exchange efliciency of the unit.

Several alternate embodiments of the spacer elements and tie elementsare illustrated in FIGURES 14, 15, and 16. The spacer and tie elementsare formed in the same general manner as the spacer and tie elementsillustrated in FIGURE 13; the basic difference being in the physicalconfiguration of the punch elements used to form the tie and spacerelements.

What is claimed is:

'1. A method of forming a fin structure from an elongated strip of finstock comprising the steps of:

(a) forming a plurality of transverse parallel slits in said fin stockdefining at least one first section and at least one second section ofsaid stock;

(b) forming a first series of tube apertures in said first section ofsaid fin stock by bending a portion of said fin stock upwardly from saidfirst section and a plurality of spacer elements having convoluted endsbent toward each other in said first section by bending a portion ofsaid fin stock upwardly from said first section and bending said edgestoward each other;

(e) forming a second series of tube apertures in said second section ofsaid fin stock by bending a portion of said fin stock downwardly fromsaid second section and a plurality of spacer elements having convolutededges bent toward each other in said second section by bending a portionof said fin stock downwardly from said second section and bending saidedges toward each other;

(d) folding one of said sections toward the other thereof such that saidtube apertures are coaligned and said spacer elements of each saidsections extend in the same direction with the spacer elements of one ofsaid sections contacting the fin stock of said other of said sections,and v (e) inserting a plurality of tubes in said tube apertures.

2. A method of forming a fin structure from an elongated strip of finstock comprising the steps of z (a) forming a plurality of co-alignedtransverse parallel slits in said fin stock defining integral tieelements between said co-aligned transverse slits and a plurality offirst sections and second sections of said stock;

(b) forming a first series of tube apertures in said first sections ofsaid fin stock by bending a portion of said fin stock upwardly from saidfirst sections and a plurality of spacer elements having convoluted endsbent toward each other in said first sections by bending a portion ofsaid fin stock upwardly from said first sections and bending said edgestoward each other;

(c) forming a second series of tube apertures in said second sections ofsaid fin stock by bending a portion of said fin stock downwardly fromsaid second sections and a plurality of spacer elements havingconvoluted edges bent toward each other in said second sections bybending a portion of said fin stock downwardly from said second sectionsand bending said edges toward each other;

(d) folding said sections such that said tube apertures are co-alignedand said spacer elements of each said sections extend in the samedirection with the spacer elements of said sections contacting the finstock of the next adjacent section and said tie elements extend betweensaid folded fin stock alternately on opposite edges of said fin stock,and

(e) inserting a plurality of tubes in said tube apertures.

3. A method of forming a fin structure from an elonv gated strip of finstock comprising the steps of:

(a) forming a plurality of transverse parallel slits in said fin stockdefining at least one first section and at least one second section ofsaid stock;

(b) forming a first series of tube apertures in said first section ofsaid fin stock by bending a portion of said fin stock upwardly from saidfirst section, a plurality of spacer elements having convoluted endsbent toward each other in said first section by bending a portion ofsaid fin stock upwardly from said first section and bending said edgestoward each other; a second series of tube apertures in said secondsection of said fin stock by bending a portion of said fin stockdownwardly from said second section, and a plurality of spacer elementshaving convoluted edges bent toward each other in said second section bybending a portion of said fin stock downwardly from said second sectionand bending said edges toward each other;

(c) folding one of said sections toward the other thereof such that saidtube apertures are co-aligned and said spacer elements of each saidsections extend in the same direction with the space-r elements of oneof said sections contacting the fin stock of said other of saidsections, and

(d) inserting a plurality of tubes in said tube apertures.

4. A method of forming a fin structure from an elongated strip of finstock comprising the steps of:

(a) forming a plurality of co-aligned transverse parallel slits in saidfin stock defining integral tie elements between said co-alignedtransverse slits and a plurality of first sections and second sectionsof said stock;

(b) bending edge portions of said tie elements toward each other to formre-enforcing edges on said tie elements;

(c) forming -a first series of tube apertures in said first sections ofsaid fin stock by bending a portion of said fin stock upwardly from saidfirst sections and a plurality of spacer elements having convoluted endsbent toward each other in said first sections by bending a portion ofsaid fin stock upwardly from said first sections and bending said edgestoward each other;

(d) forming a second series of tube apertures in said second sections ofsaid fin stock by bending a portion of said fin stock downwardly fromsaid second sections and a plurality of spacer elements havingconvoluted edges bent toward each other in said second sections bybending a portion of said fin stock downwardly from said second sectionsand bending said edges toward each other;

(e) folding said sections such that said tube apertures are co-alignedand said spacer elements of each said sections extend in the samedirection with the spacer elements of said sections contacting the finstock of the next adjacent section and said tie elements extend betweensaid folded fin stock alternately on opposite edges of said fin stockwith said reinforcing sections of said tie elements contacting adjacentsections of said fin stock, and

(t) inserting a plurality of tubes in said tube apertures.

References Cited by the Examiner UNITED STATES PATENTS 2,047,207 7/ 1936Krackowizer 29157.3 X 2,428,145 9/1947 Cook --15l 2,977,918 4/1961Kritzer 29-1573 X 3,223,153 12/1965 Simpelaur 165152 3,228,367 1/1966Donaldson 1l3ll8 JOHN F. CAMPBELL, Primary Examiner.

WHITMORE A. WILTZ, Examiner.

J. D. HOBART, Assistant Examiner,

1. A METHOD OF FORMING A FIN STRUCTURE FROM AN ELONGATED STRIP OF FINSTOCK COMPRISING THE STEPS OF: (A) FORMING A PLURALITY OF TRANSVERSEPARALLEL SLITS IN SAID FIN STOCK DEFINING AT LEAST ONE FIRST SECTION ANDAT LEAST ONE SECOND SECTION OF SAID STOCK; (B) FORMING A FIRST SERIES OFTUBE APERTURES IN SAID FIRST SECTION OF SAID FIN STOCK BY BENDING APORTION OF SAID FIN STOCK UPWARDLY FROM SAID FIRST SECTION AND APLURALITY OF SPACER ELEMENTS HAVING CONVOLUTED ENDS BENT TOWARD EACHOTHER IN SAID FIRST SECTION BY BENDING A PORTION OF SAID FIN STOCKUPWARDLY FROM SAID FIRST SECTION AND BENDING SAID EDGES TOWARD EACHOTHER; (C) FORMING A SECOND SERIES OF TUBE APERTURES IN SAID SECONDSECTION OF SAID FIN STOCK BY BENDING A PORTION OF SAID FIN STOCKDOWNWARDLY FROM SAID SECOND SECTION AND A PLURALITY OF SPACER ELEMENTSHAVING CONVOLUTED EDGES BENT TOWARD EACH OTHER IN SAID SECOND SECTION BYBENDING A PORTION OF SAID FIN STOCK DOWNWARDLY FROM SAID SECOND SECTIONAND BENDING SAID EDGES TOWARD EACH OTHER; (D) FOLDING ONE OF SAIDSECTIONS TOWARD THE OTHER THEREOF SUCH THAT SAID TUBE APERTURES ARECOALIGNED AND SAID SPACER ELEMENTS OF EACH SAID SECTIONS EXTEND IN THESAME DIRECTION WITH THE SPACER ELEMENTS OF ONE OF SAID SECTIONSCONTACTING THE FIN STOCK OF SAID OTHER OF SAID SECTIONS, AND (E)INSERTING A PLURALITY OF TUBES IN SAID TUBE APERTURES.